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Direct Measurement of Microbial Growth
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
Gram stain is a general test for characterization of bacteria and for examination of culture purity. The Gram differentiation is based upon the application of a series of four chemical reagents: primary dye, mordant, decolorizer, and counterstain. Primary dye—The purpose of the primary dye, crystal violet, is to impart a purple or blue color to all organisms regardless of their designated Gram reaction.Mordant—The crystal violet treatment followed by the application of Gram’s iodine, which acts as a mordant by enhancing the union between the crystal violet dye and its substrate by forming a complex.Decolorizer—The decolorizing solution of acetone-alcohol extracts the complex from certain cells more readily than from others.Counterstain—A safranin counterstain is applied in order to see those organisms previously decolorized by the removal of the complex.
Microbial ecology of biofiltration
Published in Joseph S. Devinny, Marc A. Deshusses, Todd S. Webster, Biofiltration for Air Pollution Control, 2017
Joseph S. Devinny, Marc A. Deshusses, Todd S. Webster
The light microscope can also be effectively used for a qualitative assessment of the microbial population in a biofilter. It may be used to identify larger prokaryotic and many eukaryotic species from their appearance. Gram stain may be employed to classify microbes according to their structure. The staining effect differs with the makeup of the cell walls of the microbes and allows typical species to be classified by their ability to retain the stain. The culture is stained with a crystal violet/iodine dye and washed with an alcohol-based decolorizer. Organisms in which the dye is removed are called gram negative. Gram-positive organisms are those for which the dye does not wash out, so they appear blue under the microscope. The tendency to stain is associated with fundamental differences in the characteristics of the cell wall. Separating the microbes into the simple classes of gram-positive and gram-negative will improve the overall understanding of the type of microbes that inhabit the biofilter. In general, gram-negative organisms are fast growing, utilize many carbon substrates, and adapt quickly to a wide variety of environments. Gram-positive organisms are generally slower growing than gram-negative organisms, are capable of degrading more recalcitrant compounds, and are more resilient to changing environmental conditions. Overall, the light microscope is a valuable tool which can supply general quantitative and qualitative information about the microorganisms inhabiting a biofilter.
Biological hazards
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
Margaret Davidson, Ryan Kift, Sue Reed
Bacteria can be categorised into gram negative or gram positive, based on a gram stain that targets the cell wall, which identifies the presence of lipopolysaccharide (LPS) or peptidoglycan (PG) in their outer cell wall (Bauman, 2012). Gram-positive bacteria typically stain purple and gram-negative bacteria, with LPS in their outer wall, stain pink. Some bacteria, such as Neisseria species and environmental isolates, can produce a gram-variable stain that is both pink and purple (Tortora, Funke and Case, 2016).
Fluorescent optotracers for bacterial and biofilm detection and diagnostics
Published in Science and Technology of Advanced Materials, 2023
Agneta Richter-Dahlfors, Elina Kärkkäinen, Ferdinand X. Choong
At present, clinical diagnostics of bacterial infections relies on culturing methods that promote growth of the microbe and/or isolation of the causative pathogen from the sample. The Gram stain is often used initially to gather preliminary information about the pathogen based on the color and morphology of bacterial colonies [28]. To obtain specific details pertaining to the pathogen’s species and virulence information, more costly molecular biology techniques are used, such as polymerase chain reaction (PCR), quantitative PCR (qPCR), fluorescence in situ hybridization (FISH), and immunoassays such as enzyme-linked immunosorbent assay (ELISA) [29–31]. With the exception of PCR, these methods tend to be time-consuming and only applicable for the viable and culturable subset of bacteria [32]. Also, these analysis only generate part of the information necessary for prescription of appropriate treatment, supplementary procedures such as antimicrobial susceptibility testing (AST) must be used to identify the antibiotic that would be most effective in clearing the infection [33–35]. Optimal treatment regimens, requiring timely and accurate identification of the causative pathogen and its antibiotic susceptibility pattern, are crucial to hinder further AMR development [36–38].
Environmental sustainability in construction: Influence of Megaterium Bacteria on the durability and mechanical properties of concrete incorporating calcined clay
Published in Mechanics of Advanced Materials and Structures, 2023
Ashish Shukla, Nakul Gupta, Nanna Sri Ramya, Kuldeep K. Saxena, Amjad Iqbal, Faramarz Djavanroodi
In this investigation, Bacillus Megaterium isolates from the Department of Biotechnology GLA University lab were utilized. Furthermore, an enrichment culture approach was used to investigated and identified this bacterial strain as shown in Figure 1. Microbes were spread out on Petri dish (NA nutrient agar dish) & total plate count technique on nutrient agar dishes for enhancement of Microorganism samples using the serial dilution approach. In a conical flask, 1.25 grams of media (Nutrient broth) were mixed with 50 milliliters of distilled water. A cotton stopper was used to cover the conical flask, which was then wrapped in aluminum foil. At 121 °C for around Twenty minutes, the mixture was disinfected by an autoclave. Water should be poured to level first in an autoclave machine before use [50]. The solvent was uncontaminated and in clear orange-yellow color upon sterilization. Every bacterial strain was given its own colony, which was then inoculated in five milliliters of nutrient broth at a pH of 12.0 and incubated at 37 °C for 12 hours at shaking conditions (130 rpm) until it grew to the desired growth. The CFU counting test was conducted after 5 milliliters of bacterial culture had been prepared. Observations are made in order to determine how much time is necessary to grow to the various concentration required for this study. The needed amount of solvent bacterial culture was then produced in a certain dosage and quantity and cement was replaced with calcined clay with different dosage [31, 51]. Culturing Technique process are shown in Figure 2. In Figure 3 shows Growth of Bacillus Megaterium and Figure 4 Shows Gram staining Result of Bacillus Megaterium Bacteria. The Gram stain test was employed to determine if the microorganisms are Gram positive or Gram negative, as well as the morphology of the cell membrane when seen under a microscopy. Some few drips of one of the main stains are applied to the smear on the microscope slide. Methyl violet & crystal violet are combined to create gentian violet. All the microorganisms are consistently stained violet by the main stain. The slide is rinsed in water after one minute of exposure to the staining solution. A few drops of Gram’s iodine are applied to the smear, and it is then left to work for one minute. A dye-iodine compound is created as a consequence in the cytoplasm. Iodine from Gram’s acts as a mordant. The slide is once again rinsed in water before being decolored with acetone or pure ethyl alcohol. For decolorization, ethyl alcohol and acetone can be mixed 1:1. Decolorization happens very quickly; for thin streaks, it shouldn’t take longer than 30 s. Acetone is a strong decolorizer that may remove the smear’s color in about 1–2 s when applied alone. Pure acetone doesn’t react as quickly as an ethanol and acetone combination. The most important step in Gram staining is decolorization, and mistakes might be made at this stage. A very short decolorization duration might result in an under-decolorized smear, whereas a very long decolorization period could result in an over-decolorized smear. The smear is immediately cleaned with water after being decolored. Finally, a few drips of a counterstain such diluted carbol fuchsin, safranin, or neutral red, are applied to the smear.